At present, magnetic devices, such as magnetic read/write heads, magnetic disks, are being widely used in data storage industry. Referring to FIG. 4, a typical magnetic read/write head, such as magneto-resistance (MR) head, generally comprises a substrate 34, shields 33, a MR element 35, a coil 32 and a yoke 31. Referring to FIG. 6, a typical magnetic disk has a substrate 10, a buffer layer 20, and a magnetic layer 30. Both above magnetic devices have some important elements, such as shield 33, MR element 35, yoke 31, magnetic layer 30, which are made of functional materials, and most of the functional materials are kinds of metal, i.e. Ni, Fe, Mn, Pt, Au, Co, Ti, Cu. Some of these metal materials are very prone to be corroded or damaged. Therefore, a protective film (overcoat) is used for preventing these elements from being corroded or damaged
In addition, surface recording density (areal density) of hard disk drivers (HDDs) has been continuously increased since last few years. The increase of areal density demands for higher signal intensity and lower flying height. Accordingly, it is also required for a thinner overcoat, for example, an ultra thin overcoat (i.e. equal or less than 3 nm) will be required for the magnetic read/write head to achieve a higher areal density (i.e. greater than 120 Gb/inch2) in the near future. Correspondingly, lower flying height with a higher rotating speed requires excellent properties of the overcoat, such as hardness, conductivity and tribology properties.
To form an overcoat for satisfying the above-mentioned requirements, a lot of forming methods have been used. Currently, the most popular methods for forming overcoats on magnetic heads are electron cyclotron resonance chemical vapor deposition (ECR CVD) and direct or secondary ion beam deposition (IBD). However, these methods have arrived at a stage where their limitation to scale down a thickness of overcoat is clearly visible, for the following reasons. One reason is that some important elements of magnetic device, such as the read/write element material, yoke and shields, become more and more sensitive to corrosion, which are aimed to have a gradually increased magnetic flux density. Another reason is that these methods use hydrocarbon as precursor, so the formed overcoat has some extent of hydrogen content (5%˜50%, atm %) and many defects (such as vacancies, or even pin hole) are formed thereon when the overcoat becomes thinner. These defects show up in the course of manufacturing, application or reliability tests for magnetic devices.
Another problem associated with these methods is that the high deposition rate results in a very short time to form an ultra thin overcoat (i.e. equal or less than 3 nm), and this makes the overcoats formed on the magnetic devices in one batch non-uniform. Additionally, the current coating machines usually utilize a shutter for blocking ion beam. The shutter normally takes about two seconds to open or close. During the course of opening or closing the shutter, there are still some ion beams bombarding the magnetic devices, which also contributes to the non-uniformity of the overcoats formed on one batch magnetic devices.
Hence it is desired to provide a method and system for forming thin film over magnetic devices which can overcome the foregoing drawbacks of the prior art.